This application is based upon and claims the benefit of priority from the prior Japanese patent Application No. 2000-325741, filed Oct. 25, 2000 the entire contents of which are incorporated herein by reference.
The present invention relates to a suspension for disc drive incorporated in an information processing apparatus, such as a personal computer, and a manufacturing method therefor.
A hard disc drive (HDD) for recording in and reading information from a rotating magnetic disc or magneto-optical disc includes a carriage that can turn around a shaft. The carriage is rotated around the shaft by means of a positioning motor. The carriage is provided with an arm (actuator arm), a suspension mounted on the distal end portion of the arm, a head portion including a slider mounted on the suspension, etc. When the disc rotates at high speed, the slider slightly lifts off the disc surface, whereupon an air bearing is formed between the disc and the slider. The suspension comprises a base portion including a base plate, a beam portion formed of a precision plate spring, a flexure fixed to the beam portion by laser welding or the like, etc. The base plate is fixed to a suspension mounting surface of the arm.
With the advance of compaction of information recorded in the disc and speed-up of the disc drive operation, the disc drive of this type has been required a shorter seek time. In order to shorten the seek time, the operation of movable portions (e.g., suspension) of the disc drive must be speeded up by reducing the weight of the movable portions and increasing the resonance frequency.
Improvement of the resonance frequency of the suspension requires a certain thickness of the base portion. If that part of the suspension of this type which covers the overall length, ranging from the base portion to the beam portion, is formed integrally from one material plate, the base portion and the beam portion have the same thickness. If a thick material is used to secure the thickness of the base portion, therefore, the beam portion is so thick that the whole suspension inevitably becomes heavy. If a thin material is used, on the other hand, the stiffness of the suspension is lowered, so that the resonance mode worsens. In these cases, the aforesaid reduction in weight and increase of the resonance frequency cannot be achieved, so that it is hard to realize high-speed seek.
Accordingly, the inventor hereof has proposed a novel suspension in which a base portion and a beam portion are connected by means of a hinge member. According to this prior art, the base portion, beam portion, and hinge member are separate components, so that materials and plate thicknesses corresponding to their respective required properties can be selected individually. Since the base portion and the beam portion are independent of each other, however, it is hard relatively to position them with high accuracy. Thus, there is still room for improvement in positioning accuracy (alignment).
Accordingly, the object of the present invention is to provide a suspension reduced in weight and capable of high-accuracy positioning between a base portion and a beam portion.
In order to achieve the above object, a suspension according to the present invention comprises a base portion, a beam portion formed of the same material as the base portion and made thinner than the base portion by partial etching, and a hinge member connecting the base portion and the beam portion to each other. The hinge member is lower in bending stiffness than the base portion and the beam portion. When a bending load is applied to the beam portion, therefore, the hinge member bends, thereby displaying a given spring characteristic.
According to this invention, the base portion and the beam portion can be made thick and thin, respectively, so that the resonance characteristic and the like can be improved, and the bandwidth of a servo mechanism can be adjusted to a higher level. Since the base portion and the beam portion can be formed from one semi-finished suspension, moreover, their relative positions can be regulated accurately.
A manufacturing method for a suspension according to the invention comprises a process for manufacturing a platelike semi-finished suspension integrally including a base portion, a beam portion, and a connecting portion connecting the base portion and the beam portion to each other, an etching process for making the beam portion thinner than the base portion by partial etching, a hinge mounting process for connecting the base portion and the beam portion by means of a hinge member, and a cutting process for separating the connecting portion from the base portion and the beam portion after the hinge mounting process.
According to this invention, the base portion and the beam portion are connected by means of the hinge member in a manner such that they are integrally included in the semi-finished suspension, so that they can be positioned accurately, and their alignment is improved.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.